[The expression of suppressor of cytokine signaling-1/3 in renal tubular epithelial cells induced by high glucose].

OBJECTIVE: To observe the morphologic changes and the expression of suppressor of cytokine signaling-1/3 (SOCS-1/3) in renal tubular epithelial cells induced by high glucose (HG) and to investigate their significance. METHODS: The renal tubular epithelial cell line (HKCs) cultured in vitro were divided into blank control group, HG group, and Janus kinase 2 inhibitor AG490 group. HKC of blank control group was cultured for 8 hours in 5.5 mmol/L glucose, and the other two groups were cultured in 300.0 mmol/L glucose or 300.0 mmol/L glucose+10 µmol/L AG490 for 2, 4, 6, 12, 24, 48 hours (n=6). The morphology and ultrastructure were observed with inversion microscope and electron microscope at different time points. Protein expression of SOCS-1/3 was assayed by immunocytochemistry and Western blotting; SOCS-1/3 mRNA was assessed by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: Under inversion microscope it was showed that 12 hours after being cultured with HG, the cells assumed a spindle-shape, with irregular protrusions, and cellular membrane became indistinguishable with prolongation of time, with increase of intracellular granules. Under the electron microscope, it was seen that there was distinct decrease in microvilli on the cell membrane and mitochondria, with an increase in rough endoplasmic reticulum. The cellular changes were not obvious in AG490 group. Furthermore, immunocytochemistry and Western blotting showed that the immunoreactivity was localized in the cytoplasm as well as in the nuclei, and there was basic expression of SOCS-1/3 protein in normal HKC (0.218±0.023, 0.337±0.009). HG was shown to induce up-regulation of the expression of SOCS-1/3 protein at 4, 6, 12, 24 hours compared with blank control group. The expression of SOCS-1 was highest at 4 hours (1.022±0.072), and that of SOCS-3 was highest at 6 hours (1.256±0.105, both P<0.01), while the expression of SOCS-1/3 protein in AG490 group was lower than that in HG group (4 hours SOCS-1: 0.589±0.167, 6 hours SOCS-3 : 0.656±0.075, both P<0.05). However, HG induced a higher expression of SOCS-1/3 mRNA at 2, 4, 6, 12 hours compared with blank control group. The expression of SOCS-1 was highest at 4 hours (1.716±0.098 vs. 0.475±0.045, P<0.05), and that of SOCS-3 was highest at 6 hours (2.848±0.116 vs. 0.749±0.086, P<0.01), while the expression of SOCS-1/3 mRNA in AG490 group was lower (4 hours SOCS-1: 0.865±0.075, 6 hours SOCS-3: 0.923±0.116, both P<0.05). CONCLUSION: HG could produce morphology and ultrastructure changes in renal tubular epithelial cell, and it induces up-regulation of SOCS-1/3 expression. These changes might be related with negative regulation of Janus kinase (JAK)/signal transducers and activators of transcription (STAT)/SOCS pathway.

[Effects of fluvastatin on the expression of Janus kinase 2/signal transducers and activators of transcription (JAK/STAT) in glomerular mesangial cells under high concentration of glucose].

OBJECTIVE: To investigate the effects of fluvastatin on activation of Janus kinase 2 (JAK2) and signal transducers and activators of transcription 1, 3 (STAT1, 3) in glomerular mesangial cells(GMCs) under high concentration of glucose. METHODS: Rat GMCs were cultured in vitro, and they were treated with glucose and fluvastatin respectively. Tyrosine phosphorylation of JAK2 (p-JAK2) expression was detected by immunoprecipitation and Western blotting analysis. The protein expressions of JAK2, STAT1, p-STAT1, STAT3 and p-STAT3 were assessed by Western blotting. The protein synthesis of transforming growth factor-beta1 (TGF-beta1) and fibronectin (FN) in the supernatants of the GMCs were determined by enzyme-linked immunoadsorbent assay (ELISA). TGF-beta1 mRNA was assessed by reverse transcription and polymerase chain reaction (RT-PCR). RESULTS: Compared with low glucose control group, the expressions of p-JAK2 (802+/-124 vs.204+/-31), p-STAT1 (2,856.6+/-337.8 vs. 617.7+/-76.2), p-STAT3 (3,049.8+/-421.3 vs. 946.7+/-141.2) and TGF-beta1 mRNA were significantly up-regulated in GMCs under high glucose medium, and the concentration of TGF-beta1 in the supernatants [(2.87+/-0.34) microg/L vs. (1.20+/-0.11) microg/L] and FN [(6.34+/-0.61) mg/L vs. (3.24+/-0.26) mg/L, both P<0.01] were higher in the supernatants. The expression levels of p-JAK2 (412+/-67), p-STAT1 (1,178.4+/-137.1), p-STAT3 (1,572.6+/-181.2) and TGF-beta1 mRNA were significantly lower in fluvastatin group than those in high glucose group. The concentration of TGF-beta1 [(1.94+/-0.27) microg/L] and FN [(4.27+/-0.33)mg/L] in the supernatants in fluvastatin group were lower than those in high glucose control group (all P<0.05). CONCLUSION: Fluvastatin can inhibit overproduction of TGF-beta1 and FN in GMCs under high concentration of glucose, the underlying mechanism may partly be attributable to its influence on phosphorylation of JAK/STAT.

[Expression and implication of osteopontin in renal cortex of diabetic rats].

OBJECTIVE: To investigate the expression and implication of osteopontin (OPN) in renal cortex of diabetic rats. METHODS: Experimental diabetes was reproduced in uninephrectomized rats by giving streptozotocin (STZ). The animals were divided into two groups: control group and diabetic group (each n=24). Immunohistochemistry and Western blotting were used to detect the protein expression of OPN, CD68, and proliferating cell nuclear antigen (PCNA). At the same time the mRNA expression of OPN was detected by in situ hybridization. RESULTS: Compared with control group, blood glucose, blood urea nitrogen (BUN), 24-hour urine protein quantum and quantification of OPN protein significantly increased while creatinine clearance rate (CCr) was significantly decreased in diabetic rat group 1, 2, 4 and 8 weeks after STZ injection. The protein of PCNA were also higher than that of control group 1 and 2 weeks after STZ injection (all P<0.05), and the increase in CD68 was observed at week 4 and week 8. CONCLUSION: Overexpression of OPN may be responsible for the proliferation of tubular cells at early stage of diabetic nephropathy and for the accumulation of macrophage at later stage.